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Cambrian

Reading: Chapter 10

The main things we want out of this chapter are 1) the evidence for Cambrian
environments and 2) the evidence severe weather leaves behind. Be sure to
note the links to other Web Sites and be sure to visit them to answer the
questions.

Background

Terms you should know:

aulacogen -

Key Concepts and Questions:

1. Breakup of the Proterozoic
supercontinent

What is
the evidence that at least one supercontinent existed in the Proterozoic?
(we'll do this in class)

To see
reconstructions of the Proterozoic supercontinent:

For
an interactive look, go here,
then click and drag the cursor across the image to run the animation.

What
is the evidence that a supercontinent broke up at about 500- 600 mya?

2. Cambrian
rocks

What
is the significance of each of these features of Lower Cambrian sandstones?

very
well rounded

almost
pure quartz

frosted
(microscopic abrasions)

large
and small scale cross-beds

What
do we conclude about how these sandstones were deposited? What does it
tell us about the tectonic setting of North America (and much of the world)?

How did
deposition change toward the end of the Cambrian? What does this tell us
about paleogeography and plate setting?

3. Episodic
events

Find
at least three indications of severe weather events left behind in Cambrian
rocks. Why would we expect the sedimentary rocks of this large epeiric sea
to be impacted primarily by large episodic storms rather than gradual deposition?

4. What
was the paleoclimate of North America during the Cambrian?

What
evidence exists to tell us about paleoclimate?

Assessment

1. Proterozoic supercontinents

You should be able to:

describe the evidence that Proterozoic supercontinents existed, and broke
up about 500-600 mya.

2. Cambrian sediments

You should be able to:

describe the origin of the Lower Cambrian sandstones and the evidence for
that origin

describe the change in depositional environments into the Middle and Late
Cambrian and the implications of that change.

3. Episodic events

You should be able to:

recognize an episodic event (such as storm surge) from its effect on the
sediment